1. Field of the Invention
This invention relates to a method for making a chalcopyrite-type compound.
2. Description of the Related Art
Chalcopyrite-type compounds, such as CuInSe2, Cu(InxGa1-x)(SeyS2-y), and Cu(InxAl1-x)(SeyS2-y) are used in the production of a semiconductor absorption layer of a solar cell due to their high optoelectric efficiency and low cost. The amount of impurities, such as the carbon content, contained in the chalcopyrite-type compound has a significantly adverse effect on the optoelectric efficiency thereof. It is desirable to manufacture a chalcopyrite-type compound having a low impurity content.
Bin Li et al. (Adv. Mater., 1999, 11, No. 17, 1456-1459) disclose a solvothermal synthesis method for making CuInSe2 nano-materials. The method involves reacting a mixture of CuCl2.2H2O, InCl3.4H2O and Se powder in a solvent of ethylenediamine at a temperature of 180° C. for 15 hr to form a precipitate. The precipitate thus formed is rinsed with an aqueous solution containing water and ethanol so as to remove by-product from the precipitate, followed by drying so as to form the chalcopyrite-type compound powder having a structure of a chalcopyrite phase. The chalcopyrite-type compound thus formed has a high carbon impurity content.
U.S. Pat. No. 7,591,990 discloses a process for making a chalcopyrite-type compound of formula M3M1A2, where M1 can be selected from Al3+, Ga3+, In3+, etc., M3 can be selected from Cu+, Ag+, etc., and A can be selected from S, Se, and Te. The process comprises reacting a compound of formula M3X with a compound of formula M2M1A2 in a coordinating solvent so as to form the chalcopyrite-type compound of formula M3M1A2, where X can be halogen atom and M2 can be Li+, Na+, K+, etc. The aforesaid process requires preparation of a ternary compound M2M1A2 as the starting material, which is more complicated as compared to a binary compound. Moreover, the reaction product of the chalcopyrite-type compound thus formed also has a relatively high impurity content. Experiments show that the chalcopyrite-type compound thus formed has a carbon impurity content of about 4.3 wt %.
The whole disclosure of U.S. Pat. No. 7,591,990 is incorporated herein by reference.